Currently available CT systems typically use a detector having silicon (Si) (p-n junction) photodiodes that are optically coupled to a scintillator. A typical size of pixels in the detector is about 1 mm. There is a tremendous dose of x-rays delivered to the detector of about 100 M photons/mm2/second (in the air without the patient). As such high photon flux is currently needed in examinations to obtain required statistics, photon counting detectors are generally not used in clinical CT systems. Hence, the detector is typically operated in an integrating mode where the detector and an x-ray generator are mounted in a continuously rotating gantry.
The use of such high photon flux may be unduly harmful to the patients. Further, the use of integration mode detectors results in generally poorer image quality than could be achieved by counting individual photons.
Therefore, there is a need for a detector that has one or more of, without being limited to, the following characteristics: 1) improved detection capabilities and faster response time to operate in a photon counting mode; 2) improved image quality; 3) spectroscopic capabilities; 4) little or no limitations in the dynamic range; 5) low sensitivity or insensitivity to afterglow; 6) low sensitivity or insensitivity to dark-current noise; and 7) provision for forming a large area, multi-slice detector using multiple detector modules.